The background description provided herein is for the purpose of generally presenting the context of the present invention. The subject matter discussed in the background of the invention section should not be assumed to be prior art merely as a result of its mention in the background of the invention section. Similarly, a problem mentioned in the background of the invention section or associated with the subject matter of the background of the invention section should not be assumed to have been previously recognized in the prior art. The subject matter in the background of the invention section merely represents different approaches, which in and of themselves may also be inventions. Work of the presently named inventors, to the extent it is described in the background of the invention section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present invention.
There is a growing literature on the use of interconnected organs-on-chips or tissue chip constructs to discover and develop drugs, determine drug safety and toxicology, develop tissue engineered constructs, and program the differentiation of induced pluripotent stem cells. In current systems presently coupling different organs together to study organ-organ and organ-drug-organ interactions, the interconnections are primarily in the form of on-chip microfluidic channels to connect organs that are on the same chip, or tubing that connects organs on different chips. The difficulty with this approach is that with the fixed channels, organs cannot be inserted, removed, or replaced because all of the organs are on a single microfluidic chip and, were a single organ to fail, all of the organs on the chip may need to be discarded. If separate organs are connected by tubing, it is difficult to make or break connections without either losing fluid or introducing bubbles. Furthermore, the volume of tubing is typically much greater than that of microfluidic channels and leads to well-known difficulties with meeting the design requirements that the total fluidic volume be properly scaled to that of the organs under study. Finally, the addition and removal of tubing from open holes present serious problems in the sterilization of the device, in that pathogens that have contaminated the surface of the device can be pushed into the fluid path by the act of insertion of the tubing. There is no easy way to sterilize such an insertion-based tubing system
Commercial fluidic systems, such as those used in trucks, trains, and industrial processes, use an interconnect that is a two-part connector with spring-actuated valves in each half, so that flow is arrested from either side when the two parts are separated. It is difficult to implement this technique in the realm of small physical dimensions, tubing diameters, tubing lengths, and small tubing volumes required for interconnected organs-on-chips. Furthermore, there is no easy way to sterilize such systems both before and after making and breaking connections.
Therefore, there is a need to interconnect separate Integrated Organ Microfluidics (TOM) modules in a sterile, low-volume manner that avoids fluid loss and introduction of air bubbles and allows ready sterilization of the interior and exterior of the fluid interconnect pathways.
In addition, in vitro cell culture is a mainstay of the drug discovery and development processes, toxicology, and biological discovery. At present, high throughput screening (HTS) uses a centralized robot to move well plates between separate single-operation stations, most importantly the fluid-handling robot. The limitation of this approach is that it is difficult or impossible to perform multiple operations on multiple well plates simultaneously. The economics of this approach is that in a system with N well plates, a single well plate can occupy any single station, e.g., fluid handing robot or scanner, for no more than 1/Nth of the duration of the experiment. This makes the long-term, physiologically realistic drug-delivery pharmacokinetics difficult to realize in an HTS well-plate environment.
Furthermore, the ability to vary the concentration of key drugs, nutrients, or toxins over an extended period of time is critical to understanding a variety of biological processes. There are a number of fields in biology and medicine wherein it is desired to perfuse two- and three-dimensional tissue constructs over long periods of time using culture media that contains concentrations of nutrients, growth factors, drugs, and toxins that may vary in time. One example of this is use of organoid culture to identify the optimum drug and drug dosing schedule and concentration to best treat the cancer of a particular patient. At present, this can be done by dissociating a biopsy sample or a resected tumor into individual cells and allowing the resulting heterogeneous population of cells to self-assemble into spherical organoids that are typically between 100 and 500 microns in diameter. A single organoid is placed in each well of a 96 or 384 well plate and is maintained in culture for intervals of time ranging between seven days and four weeks. The growth of the organoid and its response to drugs and toxins are then monitored. This is a time-consuming process because it requires daily media exchanges and carefully timed delivery of drugs to each well. The complexity of the process limits the number of wells that can be maintained, and reduces the probability of identifying the optimum drug and drug-delivery schedule. The combinatorics become even more problematic if the treatment regimen requires two drugs delivered at different times. Furthermore, it is difficult to delivery time-dependent, physiologically realistic drug delivery protocols over hours to days using a pipetting robot. Without continuous perfusion, the size of the organoid that can be supported with only daily media changes is limited, and hence there is a need to be able to continuously and independently perfuse each well of a multi-well plate.
A similar set of problems arises with the determination of the optimum sequence and concentrations for the different growth factors, nutrients, and small molecules and drugs that are delivered to induced pluripotent stem cells (iPSCs) to cause them to differentiate into a particular cellular phenotype. At present, this is done using automated fluid-handling robots, but the size and cost of the robot and the requirement that large numbers of well plates must be serviced by a single robot limits the number of combinations of growth factors, etc., that can be assayed. With pipette delivery by a central fluid-handling robot, the delivery of the required growth factors, etc., is in the form of a bolus dose, which may trigger different responses in the cells than would a steady or slowly varying concentration.
The measurement of the toxicity of drugs and environmental and industrial toxins is similarly limited by the throughput of a central fluid-handling robot that is required to both perfuse the cells or organoids or tissue constructs and deliver a range of drugs or toxins to the cells or organoids with a physiologically realistic temporal concentration profile.
Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.